1. Field of the Invention
This invention relates to a transformer, and particularly to a thin-type high power transformer for use in an inverter circuit.
2. Description of the Related Art
With improvement of display technologies, liquid crystal display (LCD) monitors have gradually become common in the field of computer or other displays. Compared to CRT monitors, LCD monitors have the advantages of slimmer profiles and better display quality with less flicker. In an LCD monitor, a backlight module has high power-driven fluorescent tubes for the required backlight system. Generally, an inverter with a driving circuit is used to drive the fluorescent tubes, and the inverter has a high-voltage transformer. Thus, in order to minimize the volume of the LCD monitor, it is necessary for the transformer used in the inverter circuit to have a thin-type structure.
A conventional transformer for the inverter circuit is generally constructed such that primary coils and secondary coils are wound around a hollow bobbin, with a core inserted into the hollow portion of the bobbin. FIG. 1a shows an embodiment of the conventional transformer for the inverter circuit, and FIG. 1b shows the cross-section of the bobbin of the transformer, with the coils wound around the bobbin.
As shown in FIG. 1a, the conventional transformer 10 for the inverter circuit has a first E-shaped core 30a and a second E-shaped core 30b. The first E-shaped core 30a and the second E-shaped core 30b can be combined to form a closed magnetic loop. Further, the conventional transformer 10 has a bobbin 50, with a primary winding window 510 and a secondary winding window 520, and pins 530 for connecting the wire of the coils to the circuit board are provided on the two ends of the bobbin 50. A flange 515 is provided between the primary winding window 510 and the secondary winding window 520, and flanges 525 are provided to separate the secondary winding window 520 into several wound areas.
In the aforementioned structure of the bobbin 50, as shown in FIG. 1b, the primary winding window 510 is used wound the primary coils 610, and the secondary winding window 520 is used wound the secondary coils 620. The wire of the secondary coils 620 has a smaller diameter and winds in multi-layers; therefore, it is necessary to separate the secondary winding window 520 into several wound areas with flanges 525 in order to prevent arcing fault resulting from the high voltage difference between two adjacent layers of coils.
In the aforementioned conventional transformer for the inverter circuit, however, the primary and secondary coils are wound on the same bobbin. This structure may result in problems.
First, in the conventional transformer, the primary winding window 510 has a limited winding range, and the wire of the primary coils has a relatively larger diameter. Therefore, if the transformer is required to have primary coils 610 with more winding turns, or an additional set of primary coils 610, the coil wound thickness will be significantly increased, compromising the transformer""s thin profile.
Further, if the power supplied by the transformer increases as is the case when at least two fluorescent tubes are driven by a single transformer, a noticeable raise in temperature occurs in the primary coils portion, possibly overheating the transformer. Increasing the wire diameter of the primary coils alleviates the temperature problem. By using a thick wire, however, the coil thickness will be increased. As a result, this method is not preferred.
Further, in conventional transformers, it is necessary to perform the mains isolation of the primary and secondary coils on the same bobbin. This may cause difficulty in voltage-resist treatment of the high-voltage coils, which increases the difficulty and cost of the transformer manufacture.
Therefore, an object of the present invention is to disclose a transformer used in the inverter circuit that solves the thickness problem.
Another object of the present invention is to disclose a transformer used in the inverter circuit that solves the temperature problem in the primary coils. Thus, overheating is prevented, and high power demands are met.
A further object of the present invention is to disclose a transformer used in the inverter circuit that corresponds to the requirement of mains isolation. With the present invention, the pressure-resistant treatment of the high-voltage coils is simplified, and a selected variety of coil wires may be applied, so that the difficulty and cost of transformer manufacture are alleviated.
The present invention discloses a transformer for an inverter circuit, comprising: a core module having a first core portion and a second core portion; a first bobbin having a first coiled portion and a first hollow portion for receiving the first core portion; a second bobbin substantially disposed parallel to the first bobbin, the second bobbin having a second coiled portion and a second hollow portion for receiving the second core portion; primary coils wound around the first coiled portion; and secondary coils wound around the second coiled portion.
In the above-mentioned transformer of the present invention, the core module may be a U-U structure constituted by two U-shaped cores, a U-I structure constituted by a U-shaped core and an I-shaped core, an L-L structure constituted by two L-shaped cores, an E-E structure constituted by two E-shaped cores, an E-I structure constituted by an E-shaped core and an I-shaped core, or a U-T structure constituted by a U-shaped core and a T-shaped core.
Further, the present invention discloses a thin-type high power transformer comprising: a first U-shaped core; a second U-shaped core; a first bobbin having a first hollow portion for inserting a part of the first U-shaped core and a part of the second U-shaped core; a second bobbin substantially disposed parallel to the first bobbin, the second bobbin having a second hollow portion for inserting a part of the first U-shaped core and a part of the second U-shaped core; primary coils wound around the first bobbin; and secondary coils wound around the second bobbin.
In the transformer of the present invention, the primary coils are wound around an independent first bobbin so that the winding area is not limited. Therefore, the winding layers of the primary coils are reduced, and the thin-type transformer may be achieved.
Further, in the transformer of the present invention, the wire diameter of the primary coils can be increased without significantly increasing the thickness of the transformer. Therefore, a selective variety of coil wires of the primary coils may be applied in the transformer of the present invention.
Further, in the transformer of the present invention, the primary coils does not stack windings, so the transformer maintains a relatively low temperature, and can be used in high power situations.
Further, in the transformer of the present invention, the primary and secondary coils are disposed parallel to each other, and no contact occurs between the coils, achieving the mains isolation requirement.
Further, in the transformer of the present invention, the primary and secondary coils are respectively wound around the first and second bobbins, so that the wound areas increase, and the transformer length is reduced.
Further, the transformer of the present invention is manufactured in a simpler process, and the costs are reduced.